Nepedia
Back to Discover
Advanced Reader
🧬

Pelvis

life science Maturity 11-13 Next article →

The pelvis is a complex anatomical region located at the base of the trunk. It sits between the abdomen and the thighs. This region includes the bony pelvis, which is a strong, basin-shaped ring of bone. It also contains the pelvic cavity, the pelvic floor, and the perineum. The pelvis is essential for human life and movement. It connects the vertebral column to the femora, which are the thigh bones. It also protects vital internal organs, such as the reproductive organs and the rectum.

Pelvis RG MR CT3d front 01
Pelvis RG MR CT3d front 01

The structure of the pelvic skeleton is divided into two main parts. These are the pelvic girdle and the pelvic spine. The pelvic spine is located at the back and consists of the sacrum and the coccyx. The pelvic girdle is formed by a pair of hip bones. Each hip bone is made of three distinct sections: the ilium, the ischium, and the pubis. In children, these three sections are separate bones. They are joined by a material called triradiate cartilage. During puberty, these sections fuse together to form a single, solid bone.

Gray238
Gray238

Inside this bony ring lies the pelvic cavity. This cavity is a space that holds the reproductive organs and the rectum. Scientists often divide this space into two sections. The greater pelvis, or false pelvis, is the area above the pelvic brim. The lesser pelvis, or true pelvis, is the area below the pelvic brim. The cavity is bounded at the top by the pelvic inlet. This inlet is bordered by several structures, including the promontory and the arcuate line of ilium. At the bottom, the cavity ends at the pelvic outlet.

Gray240
Gray240

The base of the pelvic cavity is the pelvic floor, also known as the pelvic diaphragm. This structure is made of overlapping sheets of muscle and connective tissue. It has two very different jobs that often conflict. First, it must support the weight of the organs in the abdomen. Second, it must control the openings of the rectum and urogenital organs. The pelvic diaphragm is specifically composed of the levator ani and the coccygeus muscles. Because the female genital aperture is wider, a second mechanism called the urogenital diaphragm is required to assist with closing.

Gray239
Gray239

There are significant differences between male and female pelvises due to biological needs. This is often called the "obstetrical dilemma." Humans must balance the need for efficient bipedal locomotion with the need for a wide birth canal. Because of this, the female pelvis, or gynecoid pelvis, is wider and broader. It is also lighter and thinner than the male pelvis. The female inlet is larger and oval in shape. In contrast, the male pelvis is taller, narrower, and more compact. The male inlet is more heart-shaped because the sacral promontory projects further forward.

Female pelvis
Female pelvis

These anatomical differences change how humans walk. In males, the hip bones allow the leg to move forward and backward in a single plane. In females, the leg must swing forward and then inward. This movement happens because the pivoting head of the femur moves in a different plane. This specific movement creates the characteristic swinging of the hips seen in the female gait. The male pelvis is optimized for walking, while the female pelvis is optimized for childbirth. The angle of the pubic arch also differs, being about 70 degrees in males and 90 to 100 degrees in females.

Gray321
Gray321

The pelvis also serves as a vital anchor for the muscles used for posture and movement. It is a very stable and rigid structure. This stability is necessary to transfer weight from the axial skeleton to the lower limbs. The pelvic girdle is connected at the front by the pubic symphysis. At the back, it connects to the sacrum at the sacroiliac joints. This forms a ring that allows very little mobility. This rigidity is a requirement for transmitting the heavy loads of the body to the legs during standing and walking.

Anterior Hip Muscles 2
Anterior Hip Muscles 2
651 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (11)
File:Pelvis RG MR CT3d front 01.jpg
Pelvis RG MR CT3d front 01.jpg
File:Gray238.png
Gray238.png
File:Gray240.png
Gray240.png
File:Gray239.png
Gray239.png
File:Female pelvis.png
Female pelvis.png
File:Gray321.png
Gray321.png
File:Gray389.png
Gray389.png
File:Posterior Hip Muscles 1.PNG
Posterior Hip Muscles 1.PNG
File:Anterior Hip Muscles 2.PNG
Anterior Hip Muscles 2.PNG
File:Posterior Hip Muscles 3.PNG
Posterior Hip Muscles 3.PNG
File:Falcarius pelvis.jpg
Falcarius pelvis.jpg
More to explore

✨ What else?

Related topics you might enjoy

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.